Tanks are used in innumerable applications for storing fluids, especially liquids, of different kinds. When a fluid has been emptied from the tank, it is often desired to clean the tank. The cleaning should remove residues for a number of reasons such as for avoiding cross contamination, for avoiding build up of contamination layers and for preparing the tank for another batch of fluid. The cleaning is typically done by flushing the inside walls of the tank with a cleaning liquid and different devices for performing such flushing is known within the art. Tanks are typically provided with a flushing device (often permanently installed) for performing the tank cleaning.
One type of known flushing devices comprises a pipe fitted, at one end, with a housing provided with a number of nozzles arranged on a hub. The end of the pipe provided with the housing is arranged inside the tank and cleaning liquid is fed through the pipe to the nozzles from which it is ejected towards the tank inside walls. Typically, to optimize the coverage of the tank inside, the housing rotates about a longitudinal axis of the pipe while the hub and the nozzles rotate about an axis perpendicular to the longitudinal axis of the pipe. The jets from the nozzles together form a cleaning pattern on the inside walls of the tank.
Typically, the pipe of the flushing device is soiled by the fluid stored in the tank. Therefore, in connection with the tank cleaning, it is desirable if the flushing device has a function for cleaning also the pipe itself. SE 534 731 discloses a flushing device like the one described above. It comprises a flush head provided with a number of nozzles of which at least one is angled in relation to the pipe such that the pipe is hit by a jet from this nozzle during at least a part of the rotation of the flush head. The pipe is hit by the jet annularly and at a certain height, i.e. at a certain distance from a fixed reference point. An annular pipe area arranged about this height is thereby effectively cleaned. However, the rest of the pipe area is less effectively cleaned. Further, angling of one nozzle in relation to the others result in a change of the cleaning pattern on the tank inside walls which may result in a less effective cleaning of the inside of the tank.